This invention relates generally to an improved method and apparatus for the treating of railroad ballast, and more particularly to a manner of removing the ballast.
Any number of approaches have been developed in the past for the purpose of undercutting, i.e., for the removal of ballast from between railroad ties or from beneath the ties or from both shoulder sections by mechanical means. The types of machinery available generally fall into the category of undercutters, plows, plows and sleds, cribbers and shoulder cleaners. Undercutters are generally based on an endless-chain principle and in most machines the old ballast can be reclaimed, cleaned and returned to the track in a single operation. The plow is a solid metal V-shaped blade having wings and a towing harness to facilitate drawing of the plow under the track structure either by an engine or a stationary pull car. However, with the use of plows there is no acceptable way at the present time to recover any portion of the old ballast for reuse in the track. A sled is usually used in connection with the plow for distribution of a uniform layer of ballast under the ties in advance of surfacing units. Cribbers are much smaller than undercutters and have an endless-chain arm which can remove the old ballast from beneath the ties for a distance half the length of the tie, there being two machines which must work opposite one another to completely remove the crib. (Cribbers reaching along the full length of the tie are also available.) The shoulder and crib material can then be cleaned and returned to the track area by the use of shoulder-cleaning machines, or may be plowed off and wasted or used to restore the subgrade. This technique is slow, tedious and expensive and is seldom used except in isolated short areas. The plow and sled or cribber and shoulder cleaner are not in the true sense undercutters since this equipment is designed to skeltonize the track of the contaminated ballast so as to leave the skeltonized track on a relatively smooth level subgrade. Ballast material is then deposited on the subgrade thereby resulting in full replacement of the ballast section. Use of such devices also is slow, tedious and expensive.
The presence of any number of conditions may generally determine when to use undercutters as, for example: when the ballast becomes so contaminated and fouled that it will not properly drain water, when the surface of the track deteriorates to such an extent as to affect its holding characteristics, and when track joints are found to be pumping mud. Evidence of crushed railroad ties and corrugated rails likewise indicate the need for undercutting. The need to conserve the use of ballast and to change the type of ballast can be satisfied by undercutting, as well as a need to restrict overhead or ground structures. And, the proximity of adjacent side tracks and structures as, for example, switches and turnouts, may determine the particular type of undercutting operation required.
In the past when an undercutter, plow or out-of-face surface machine reached a turnout, the ballast removal operation ceased because of the obstacles encountered at such a track location. This resulted eventually in a sagging condition at the turnout compared to the adjoining track, as well as a poor surface end line. Also, the unremoved fouled ballast at the turnout resulted in poor drainage, poor riding conditions and expensive maintenance. Switch undercutters and switch tampers are now available and these machines can perform the work to rehabilitate turnouts either in a programmed undercutting area or only for reconditioning the switches. One switch undercutter machine is an on-track unit having an endless chain equipped with cutting and raking teeth. The chain works on a horizontal plane and its race is supported by a horizontal arm. The undercutting arm can be raised and lowered, swung transversely to place it at an angle or parallel with the track, and can be moved laterally. These movements enable the machine to undercut turnouts and multiple tracks placed on close track centers. It undercuts several inches below the bottom of the ties and rakes the ballast out to the shoulder of the track.
However, operation of a switch undercutter is expected to require a crew of nine or ten men. The turnout is first undercut from a point just ahead of the head block to beyond the switch ties. Since the fouled ballast removed must be wasted, it is plowed off to the side in open-track territory or a back hoe is used to excavate a trench alongside the track into which the waste material is placed when next to adjacent trackage. While the switch is in a skeltonized condition, the ties are renewed and respaced as necessary and the rail anchors are adjusted. New ballast is then unloaded and the turnout is raised, tamped and lined. As a result, about 6 inches of clean ballast is placed under the ties and the turnout is raised sufficiently to conform to that of the adjoining track.
Of the different undercutting and ballast removal equipment available today, the plow and the chain are probably most widely used. The endless-chain type machine, however, is limited in the amount of ballast material capable of being removed as well as the rate at which the machine is capable of traveling so that the production rate for such machine is relatively low. And, besides the inability of recovering any portion of the fouled ballast for reuse when a plow undercutter is used, such a device is generally incapable of undercutting at turnouts since it is pulled by a bridle arrangement. Also, it is difficult to control direction of the plow if any appreciable amount of undercutting is to be done since keels are provided for counteracting the side forces. And, many plow types use long front runners to raise the ties and rail a considerable distance above the ballast and then plow or scrape the ballast to the side, returning the ties and track to the scraped surface.